A porous material having pores has been used in various fields for increasing a surface area of an article, buffering a pressure to be applied to an article, adjusting fluidity during friction, or the like. For example, the porous material may include an abrasive pad used for planarization of a semiconductor wafer or display glass, a carbon electrode manufactured by using a binder and a foaming agent, a polymer film or sheet used for improving an absorbent property or wrinkle resistance, or the like.
In most cases, a surface of the porous material includes pores or is not flat. Therefore, it is not easy to form a layer of an adhesive or pressure sensitive adhesive on the surface of the porous material so as to be attached to other objects. This is because the porous surface or the non-flat surface causes a great decrease in wettability of a polymer which is a material of an adhesive or pressure sensitive adhesive.
It is possible to increase wettability of the adhesive or pressure sensitive adhesive with respect to the surface of the porous material by adjusting properties of the polymer. However, along with the increase in wettability, cohesiveness of the adhesive is decreased, and thus, even if a weak shear strength is applied thereto, the adhesive or pressure sensitive adhesive is easily separated from an adhered surface.
Therefore, it is not easy to firmly attach the porous material to an adhered surface, especially when an area of an adherent is increased.